Managing electric current allocation between charging equipment for charging electric vehicles

ABSTRACT

A first and second charging equipment for charging electric vehicles share a current capacity. A controller coupled with the first and second charging equipment limits a total amount of current drawn through the first charging equipment and the second charging equipment to not exceed the current capacity. The controller communicates a first and second current limit to the first and second charging equipment respectively to cause a first and second electric vehicle to limit their current draw to not exceed the first and second current limit respectively. A sum of current to be drawn at the first and second current limit does not exceed the current capacity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 14/956,264,filed Dec. 1, 2015, which is a continuation of U.S. Pat. No. 9,201,408,filed Jun. 6, 2014, which is a continuation of U.S. Pat. No. 9,201,407,filed Jul. 23, 2013, which is a continuation of U.S. Pat. No. 8,502,500,filed Sep. 6, 2011, which is a division of U.S. Pat. No. 8,013,570,filed Jul. 23, 2009, which are each hereby incorporated by reference.

BACKGROUND

Field

Embodiments of the invention relate to the field of electric vehiclecharging stations, and more specifically to managing electric currentallocation between charging equipment for charging electric vehicles.

Background

Charging stations are typically used to provide charging points forelectric vehicles (e.g., electric battery powered vehicles,gasoline/electric battery powered vehicle hybrid, etc.). Chargingstations may be located in designated charging locations (e.g., similarto locations of gas stations), parking spaces (e.g., public parkingspaces and/or private parking space), etc. Most electric plug-invehicles have on board chargers that accept either 110V, 220V (230V inEurope) and draw power at current levels from 10 A to 70 A.

Electrical service (wiring and circuit protection) of the appropriaterating is typically brought to each of the charging stations. Multiplecharging stations can be on the same electrical circuit, which isconnected to an electrical breaker panel that is fed by a service dropfrom a local utility distribution transformer.

In a typical charging station installation, the size of the wiring, thebreaker, and the service drop associated with a circuit is determined bysimply summing the current ratings of each of the charging stations onthe circuit (thus, a maximum use scenario is assumed). In this way, itcan be assured that if all of the charging stations are in use at thesame time, and all are delivering their maximum current, the breakerwill not trip and the wiring will not overheat.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 illustrates an exemplary charging system according to oneembodiment of the invention;

FIG. 2 illustrates an exemplary embodiment of the charging stationillustrated in FIG. 1 according to one embodiment of the invention;

FIG. 3 illustrates an exemplary network of charging stations that areeach wired to the same circuit breaker according to one embodiment ofthe invention;

FIG. 4 illustrates an exemplary series of messages exchanged between acharging station and a circuit sharing controller during allocation ofelectric current according to one embodiment of the invention;

FIGS. 5A-B are flow diagrams illustrating exemplary operations for acircuit sharing process based on load sharing according to oneembodiment of the invention;

FIG. 6 is a flow diagram illustrating exemplary operations fordynamically adjusting electric current allocations of multiple chargingstations on the same electrical circuit when a charging station nolonger requests an allocation of current according to one embodiment ofthe invention;

FIG. 7 is a flow diagram illustrating exemplary operations forperforming a circuit sharing process that is based on time sharingaccording to one embodiment of the invention;

FIG. 8 is a flow diagram illustrating exemplary operations forcyclically reallocating electric current in a time sharing processaccording to one embodiment of the invention;

FIG. 9 is a flow diagram illustrating exemplary operations performed ina circuit sharing process that is based on time sharing when a chargingstation no longer requests an allocation of current according to oneembodiment of the invention; and

FIG. 10 illustrates an exemplary embodiment of a circuit sharingcontroller according to one embodiment of the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knowncircuits, structures and techniques have not been shown in detail inorder not to obscure the understanding of this description. Those ofordinary skill in the art, with the included descriptions, will be ableto implement appropriate functionality without undue experimentation.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.Rather, in particular embodiments, “connected” may be used to indicatethat two or more elements are in direct physical or electrical contactwith each other. “Coupled” may mean that two or more elements are indirect physical or electrical contact. However, “coupled” may also meanthat two or more elements are not in direct contact with each other, butyet still co-operate or interact with each other.

The techniques shown in the figures can be implemented using code anddata stored and executed on one or more computing devices (e.g.,electric vehicle charging stations, electric vehicle charging stationnetwork servers, circuit sharing controllers, etc.). As used herein, acharging station is a piece of equipment, including hardware andsoftware, to charge electric vehicles. Such computing devices store andcommunicate (internally and with other computing devices over a network)code and data using machine-readable media, such as machine storagemedia (e.g., magnetic disks; optical disks; random access memory; readonly memory; flash memory devices; phase-change memory) and machinecommunication media (e.g., electrical, optical, acoustical or other formof propagated signals—such as carrier waves, infrared signals, digitalsignals, etc.). In addition, such computing devices typically include aset of one or more processors coupled to one or more other components,such as a storage device, one or more input/output devices (e.g., akeyboard, a touchscreen, and/or a display), and a network connection.The coupling of the set of processors and other components is typicallythrough one or more busses and bridges (also termed as bus controllers).The storage device and signals carrying the network traffic respectivelyrepresent one or more machine storage media and machine communicationmedia. Thus, the storage device of a given computing device typicallystores code and/or data for execution on the set of one or moreprocessors of that device. Of course, one or more parts of an embodimentof the invention may be implemented using different combinations ofsoftware, firmware, and/or hardware.

Electric vehicle charging stations (hereinafter “charging stations”) arecoupled with an electric vehicle charging station network server(hereinafter “server”). Multiple charging stations are wired to the sameelectrical circuit such that if each charging station were operating atfull load the capacity of the electrical circuit would be exceeded. Adynamic circuit sharing process is performed to prevent the capacity ofthe electrical circuit from being exceeded while permitting the chargingstations that share that electrical circuit to draw electric currentthrough that electrical circuit for at least some amount of time. In oneembodiment the circuit sharing process is controlled by a circuitsharing controller coupled with the charging stations.

The present invention will now be described in detail with reference tothe drawings, which are provided as illustrative examples of theinvention so as to enable those skilled in the art to practice theinvention. Notably, the figures and examples below are not meant tolimit the scope of the present invention to a single embodiment, butother embodiments are possible by way of interchange of some or all ofthe described or illustrated elements.

FIG. 1 illustrates an exemplary charging system according to oneembodiment of the invention. The charging system illustrated in FIG. 1includes the charging station 120, which is coupled with the power grid130 over the power line 135. The power grid 130 can be owned and/oroperated by local utility companies or owned and/or operated by privatepersons/companies. The power line 135 is wired to the circuit breaker125, which can be separate and remote from the charging station 120. Inone embodiment, the circuit breaker 125 is inaccessible to vehicleoperators (e.g., the vehicle operator 145). As will be described ingreater detail with reference to FIG. 3, in some embodiments additionalcharging stations besides the charging station 120 are wired on the samepower line 135 to the circuit breaker 125 (i.e., multiple chargingstations share the same electrical circuit).

Operators of electric vehicles (e.g., the electric vehicle operator 145)can use the charging station 120 to charge their electric vehicles(e.g., the electric vehicle 110). For example, the electricity storagedevices (e.g., batteries, supercapacitors, etc.) of electric vehicles(e.g., electric powered vehicles, gasoline/electric powered vehiclehybrids, etc.) may be charged through use of the charging station 120.It should be understood that electric vehicle operators may includedrivers of electric vehicles, passengers of electric vehicles, and/orservice personnel of electric vehicles. In one embodiment, the operatorsof electric vehicles provide their own charging cord to charge theirelectric vehicle (e.g., the charging cord 140 belongs to the electricvehicle operator 145), while in other embodiments the charging station120 includes an attached charging cord (e.g., the charging cord 140 isfixably attached to the charging station 120).

In one embodiment, the charging station 120 can charge in a dual mode atdifferent voltages (e.g., 120V and 240V). By way of example, a fixablyattached charging cord is typically used in a higher voltage mode (e.g.,240V) and an unattached charging cord is typically inserted into a powerreceptacle of the charging station 120 in a lower voltage mode (e.g.,120V).

In some embodiments, the flow of electrical power can be in eitherdirection on the power line 135. In other words, the electric vehicle110 can be charged from the power grid 130 or the power grid 130 canreceive power from the electric vehicle 110 (hereinafter referred to as“vehicle-to-grid” (V2G). V2G is particularly attractive for electricvehicles that have their own charging devices, such as battery electricvehicles with regenerative braking and plug-in hybrid vehicles. Thus, insome embodiments of the invention, the electric vehicle 110 may consumeelectricity from the power grid 130 as well as transfer electricity tothe power grid 130.

The charging station 120 is also coupled with the server 180 through thedata control unit (DCU) 170. The DCU 170 acts as a gateway to the server180 and relays messages and data between the charging station 120 andthe server 180. The charging station 120 exchanges messages and datawith the DCU 170 over the LAN (Local Area Network) link 175 (e.g., WPAN(Wireless Personal Area Network) (e.g., Bluetooth, ZigBee, etc.), orother LAN links (e.g., Ethernet, PLC (Power Line Communication), WiFi,etc.). The DCU 170 exchanges messages and data with the server 180 overthe WAN link 185 (e.g., Cellular (e.g., CDMA, GPRS, etc.) WiFi Internetconnection, Plain Old Telephone Service, leased line, etc.). Accordingto one embodiment of the invention, the DCU 170 can be included as partof a charging station (e.g., the charging station 120 or a differentcharging station coupled with the server 180). In other embodiments theDCU 170 is be a separate device not part of a charging station. In someembodiments, the charging station 120 is coupled with the server 180directly (i.e., without a connection through a DCU).

The server 180 provides services for multiple charging stations (e.g.,authorization service, accounting services, etc.). As will be describedin greater detail later herein, in one embodiment the server 180controls and manages the electric current allocation for multiplecharging stations through one or more messages sent to those chargingstations (e.g., a message can indicate whether a charging station ispermitted to allow electric current to flow on the power line 135). Inother embodiments the DCU 170 can control and manage the electriccurrent allocation of charging stations.

The server 180 stores vehicle operator information (e.g., operatoraccount information, operator contact information (e.g., operator name,street address, email address, telephone number, etc.)) and chargingstation configuration information. The charging station configurationinformation can include information related to each charging station andthe charging sessions on the charging stations. For example, for eachcharging station, the server 180 can store the following: the wiringgroup the charging station belongs to (as used herein, a wiring groupcorresponds to the physical wiring connection to a common circuitbreaker), the electrical circuit capacity of the wiring group (e.g., thebreaker size), a trip margin used to prevent false circuit breakertrips, a quantity of electric current that is currently being consumedor transferred, whether a vehicle is plugged into the charging station,the length of charging sessions (current and past), etc.

In one embodiment of the invention, the server 180 includes a subscriberportal (available through the Internet) which allows subscribers (ownersand operators of electric vehicles) to register for service (which mayinclude providing information regarding their electric vehicles,providing payment information, providing contact information, etc.) andperform other functions (e.g., pay for charging sessions, determineavailability of charging stations, check the charging status of theirelectric vehicle(s), etc.). In addition, the server 180 may include ahost portal (available through the Internet) which allows owners oradministrators of the charging station 120 (and other charging stations)to configure their charging stations and perform other functions (e.g.,determine average usage of charging stations, etc.). The host portal mayalso be used to configure the circuit sharing process described herein.Charging stations may also be configured using other means in someembodiments of the invention (e.g., through Telnet, user interface,etc.).

The charging station 120 controls the application of electricity betweenthe charging point connection 155 and the power grid 130 by energizingand de-energizing the charging point connection 155. In one embodiment,the server 180 instructs the charging station 120 when to energize thecharging point connection 155 and can also instruct the charging station120 to de-energize the charging point connection 155. In one embodiment,the charging point connection 155 is a power receptacle or circuitry foran attached charging cord (e.g., thus the charging station 120 canenergize/de-energize the power receptacle or the circuit for an attachedcharging cord). The power receptacle can be any number of types ofreceptacles such as receptacles conforming to the NEMA (NationalElectrical Manufacturers Association) standards 5-1 5, 5-20, and 14-50or other standards (e.g., BS 1363, CEE7, etc.) and may be operating atdifferent voltages (e.g., 120V, 240V, 230V, etc.).

Electric vehicle operators can request charging sessions for theirelectric vehicles in different ways in different embodiments of theinvention. As one example, the electric vehicle operator 145 can use thecommunication device 150 to initiate and request a charging session forthe electric vehicle 110. The communication device 150 may be a WLAN orWPAN device (e.g., one or two-way radio-frequency identification (RFID)device, mobile computing device (e.g., laptops, palmtop, smartphone,multimedia mobile phone, cellular phone, etc.)), ZigBee device, etc. Thecommunication device 150 communicates unique operator-specificinformation (e.g., operator identification information, etc.) to thecharging station 120 (either directly or indirectly through the server180). In some embodiments, electric vehicle operator 145 may use thecommunication device 150 to monitor the charging status of the electricvehicle 110. In one embodiment of the invention, the communicationdevice 150 may be coupled with the electric vehicle 110.

As another example, the electric vehicle operator 145 may interact witha payment station coupled with the charging station 120, which may thensend appropriate instructions to the charging station 120 regarding thecharging of the vehicle 110 (e.g., instructions to energize the chargingpoint connection 155). The payment station may function similarly to apayment station for a parking space. In addition, a payment stationcoupled with the charging station 120 may be used both for parkingpayment and charging payment. As yet another example, the electricvehicle operator 145 may use a user interface of the charging station120 to request a charging session for the electric vehicle 110.

FIG. 2 illustrates an exemplary embodiment of the charging station 120according to one embodiment of the invention. The charging station 120includes the charging point connection 155, the charging station controlmodules 205, the electricity control device 210, the current measuringdevice 220, the RFID reader 230, the user interface 235, the displayunit 240, and one or more transceivers 250 (e.g., wired transceiver(s)(e.g., Ethernet, power line communication (PLC), etc.) and/or wirelesstransceiver(s) (e.g., 802.15.4 (e.g., ZigBee, etc.), Bluetooth, WiFi,Infrared, GPRS/GSM, CDMA, etc.)). It should be understood that FIG. 2illustrates an exemplary architecture of a charging station, and other,different architectures may be used in embodiments of the inventiondescribed herein. For example, some implementations of charging stationsmay not include a user interface, an RFID reader, or a connection to anetwork.

The RFID reader 230 reads RFID tags from RFID enabled devices (e.g.,smartcards, key fobs, etc., embedded with RFID tag(s)) of operators thatwant to use the charging station 120. For example, the operator 145 maywave/swipe the mobile communication device 150 (if an RFID enableddevice) near the RFID reader 230 to request a charging session from thecharging station 120.

The RFID reader 230 passes the information read to one or more of thecharging station control modules 205. The charging station controlmodules 205 are programmed to include instructions that establishcharging sessions with the vehicles. In one embodiment, the operator 145is authenticated and authorized based on the information the RFID reader230 receives. While in one embodiment of the invention the chargingstation 120 locally stores authorization information (e.g., in theconfiguration/operator data store 270), in other embodiments of theinvention one of the charging station control modules 205 transmits anauthorization request to a remote device (e.g., the server 180) via oneof the transceivers 250. For example, an authorization request istransmitted to the data control unit 170 over a WPAN transceiver (e.g.,Bluetooth, ZigBee) or a LAN transceiver. The data control unit 170relays the authorization request to the server 180.

In some embodiments, in addition to or in lieu of vehicle operatorsinitiating charging sessions with RFID enabled devices, vehicleoperators may use the user interface 235 to initiate charging sessions.For example, vehicle operators may enter in account and/or paymentinformation through the user interface 235. For example, the userinterface 235 may allow the operator 145 to enter in a username/password(or other information) and/or payment information. In other embodimentsof the invention, vehicle operators may request charging sessionsthrough devices remote to the charging station 120 (e.g., paymentstations coupled with the charging stations). In some embodiments, thevehicle operators can also define a privilege or priority level of theirrequest (e.g., charge immediately, charge anytime, etc.) which mayaffect the cost of that charging session.

One or more of the charging station control modules 205 cause thecharging point connection 155 to be energized. For example, one or moreof the charging station control modules 205 cause the electricitycontrol device 210 to complete the connection of the power line 135 tothe power grid 130. In one embodiment, the electricity control device210 is a solid-state device that is controlled by the charging stationcontrol modules 205 or any other device suitable for controlling theflow of electricity. As will be described in greater detail laterherein, in some embodiments the electricity control device 210 includescircuitry to variably control the amount of power draw (e.g. Pulse WidthModulation (PWM) circuitry). In some embodiments, the charging stationcontrol modules 205 cause the charging point connection 155 to beenergized or de-energized based on messages received from the server 180and/or from the DCU 170.

The current measuring device 220 measures the amount of current that isflowing on the power line 135 through the charging point connection 155(e.g., between the vehicle 110 and the charging station 120). In someembodiments, in addition to electric vehicles being able to be chargedfrom the power grid 130, these electric vehicles can be a source ofelectric power to be transferred to the power grid 130 (vehicle-to-grid(V2G)). While in one embodiment of the invention the current measuringdevice 220 measures flow of current, in an alternative embodiment of theinvention the current measuring device 220 measures power draw. Thecurrent measuring device 220 may include or be coupled with an inductioncoil or other devices suitable for measuring current. The currentmeasuring device 220 is coupled with the charging station controlmodules 205. The charging station control modules 205 are programmedwith instructions to monitor the current data output from the currentmeasuring device 220 and to calculate the amount of electricity beingused over a given time period.

The display unit 240 is used to display messages to the operator 145(e.g., charging status, confirmation messages, error messages,notification messages, etc.). The display unit 240 may also displayparking information if the charging station 120 is also acting as aparking meter (e.g., amount of time remaining in minutes, parkingviolation, etc.). The configuration/operator data store 270 storesconfiguration information which may be set by administrators, owners, ormanufacturers of the charging station 120.

While FIG. 1 illustrates a single charging station 120, it should beunderstood that many charging stations may be networked to the server180 (through one or more data control units) and/or to each other. Inaddition, multiple charging stations can share the same circuit, becoupled with the same circuit breaker, and have their power drawcontrolled by the same circuit sharing controller in some embodiments.

FIG. 3 illustrates an exemplary network of charging stations that sharethe same electrical circuit and circuit breaker according to oneembodiment of the invention. The charging station network 300 includesthe charging stations 120, 310, 315, 325, and 330 coupled with circuitsharing controller 305. The charging stations 120, 310, 315, 325, and330 are each wired to the circuit breaker 125 and share the same powerline 135. Thus, the charging stations 120, 310, 315, 325, and 330 sharethe same electrical circuit. The charging stations 120, 310, 315, 325,and 330 are in the wiring group 350.

As will be described later herein, in one embodiment the circuit sharingcontroller 305 controls and manages the power draw of the chargingstations in the wiring group 350 through one or more messages to thosecharging stations. The circuit sharing controller 305 can implemented onthe server 180, the DCU 170, or a separate device coupled with thecharging stations of the wiring group 350. The charging stations 120,310, and 325 are directly coupled with the circuit sharing controller305 via the LAN links 175, 360, and 370 respectively. The chargingstation 315 is indirectly coupled with the circuit sharing controller305 through the LAN link 365 to the charging station 120 which is itselfdirectly coupled with the circuit sharing controller 305 via the LANlink 175. The charging station 330 is indirectly coupled with thecircuit sharing controller 305 through the LAN link 375 to the chargingstation 325 which is itself directly coupled with the circuit sharingcontroller 305 over the LAN link 370.

Although not illustrated in order not to confuse understanding of theinvention, the charging stations 120, 310, 315, 325, and 330 are alsopart of the same radio group (as used herein, a radio group is acollection of one or more charging stations that collectively has asingle connection to an electric vehicle charging station networkserver). It should be understood that the network architectureillustrated in FIG. 3 is exemplary and different embodiments can havedifferent network architectures. For example, wiring groups can includemembers that are associated with different circuit sharing controllersand a single circuit sharing controller can manage charging stations inmultiple wiring groups. As another example, each charging station canhave a direct connection with the circuit sharing controller 305.

As illustrated in FIG. 3, each of the charging stations 120, 310, 315,325, and 330 share the same circuit (they all receive power through thepower line 135) and are all each coupled with the same circuit breaker125. It should be understood that if activity at one of the chargingstations 120, 310, 315, 325, and 330 causes the circuit breaker 125 totrip then all of the charging stations will lose their electricalconnection with the power grid 130 (i.e., they all lose power). Thus,upon the circuit breaker 125 tripping, any charging sessions currentlyin progress on the charging stations 120, 310, 315, 325, and 330 will beinterrupted.

As illustrated in FIG. 3, multiple charging stations (charging stations120, 310, 315, 325, and 330) share the same electrical circuit and arewired to the same circuit breaker (circuit breaker 125). It should beunderstood that all of the charging stations in the wiring group 350 maynot be delivering their maximum charging output at a given time. Forexample, some of the charging stations may be idle (not being used). Asanother example, charging stations may not supply their maximum chargingoutput when an electric car has been fully charged or nearly charged. Inorder to reduce the cost to install power distribution infrastructure,the size of the circuit is chosen such that the circuit supportssomething less than a complete utilization of the charging stations (interms of electric current draw) on the circuit. Thus, in one embodiment,the circuit will be overloaded and the circuit breaker 125 will trip ifall of the charging stations in the wiring group 350 are each supplyingcurrent according to their maximum rating. In other words, the circuitwill overload if there is a complete utilization of all the chargingstations in the wiring group 350. Of course, it should be understoodthat the circuit can be overloaded by a smaller amount of utilization ofthe charging stations in the wiring group 350.

In order to prevent the electrical circuit from overloading and thecircuit breaker 125 from tripping, the charging stations in the wiringgroup 350, in cooperation with the circuit sharing controller 305,dynamically manage their power delivery such that the total electriccurrent draw on the electrical circuit does not exceed a capacity of theelectrical circuit (or a smaller amount of the capacity to protectagainst spurious breaker trips) while allowing for multiple chargingstations to be wired to the same physical electrical circuit.

As previously described, the circuit sharing controller 305 can instructthe charging stations to commence or cease drawing electric current forcharging sessions. In some embodiments, the circuit sharing controller305 limits the power draw of individual charging stations on the sameelectrical circuit such that the total power consumed by all of thecharging stations on that electrical circuit does not exceed thecapacity of the electrical circuit.

In one embodiment, the circuit sharing controller 305 dynamicallyallocates electric current to the charging stations in the wiring group350 (at least those who are requesting electric current allocation)based on at least an amount of electric current presently allocated onthe electrical circuit (e.g., the amount of electric current presentlyallocated to ones of the charging stations in the wiring group 350) insuch a way to prevent the capacity of the electrical circuit from beingexceeded while permitting each of those charging stations to drawelectric current through the electrical circuit for at least some amountof time. The electric current allocation of the individual chargingstations can be dynamically adjusted (either increased or decreased)based on a set of one or more factors (e.g., the number of chargingstations requesting electric current allocation, the amount of electriccurrent presently allocated on the electrical circuit, the capacity ofthe electrical circuit, the amount of electric current requested, andone or more charging session attributes (e.g., charging sessionduration, the type of account associated with the charging session(e.g., privilege of the account), percentage of charge complete,percentage of charge remaining, battery temperature of the electricvehicle, time remaining on the charging session, priority of thecharging session, etc.)).

The allocation of electric current for charging stations on the samecircuit can be performed differently in different embodiments of theinvention. In one embodiment, the circuit sharing controller 305controls the amount of electric current that each of the chargingstations in the wiring group 350 can draw through a series of messagesexchanged between those charging stations and the circuit sharingcontroller 305.

FIG. 4 illustrates an exemplary series of messages exchanged between thecharging station 120 and the circuit sharing controller 305 duringallocation of electric current for the charging station 120 according toone embodiment of the invention. FIG. 4 will be described with referenceto FIG. 3, however it should be understood that the operations describedwith reference to FIG. 4 can be performed by embodiments of theinvention other than those discussed with reference to FIG. 3.

At operation 4.1, the charging station 120 transmits an electric currentallocation request message to the circuit sharing controller 305. In oneembodiment, the electric current allocation request message includes anamount of current that the charging station 120 would like to draw fromthe power grid 130 (the power grid 130 is not shown in FIG. 4 in ordernot to obscure understanding of the invention). The amount of electriccurrent requested can vary. For example, upon an initial chargingsession request, the amount of current can be the maximum amount ofcurrent rated for the charging point connection of the charging station.However, after charging has been complete (or substantially complete),the charging station may send an electric current allocation request forless than the maximum amount of current rated for the charging pointconnection. The charging stations transmit the electric currentallocation requests when the amount of current changes (e.g., when anelectric vehicle is plugged into the charging station, the electricvehicle has been completely or substantially completely charged), thecharging station has timed-out waiting for an acknowledgement messagefrom the circuit sharing controller 305, and when it powers on and/orundergoes a system restart.

At operation 4.2, the circuit sharing controller 305 transmits anacknowledgment message to the charging station 120 in response toreceiving the electric current allocation request of operation 4.1. Asdescribed above, if the charging station 120 does not receive theacknowledgment message in response to the electric current allocationrequest within a timeout interval, it will resend the request message.In some embodiments the acknowledgement message transmitted in operation4.2 is optional.

The circuit sharing controller 305 processes the electric currentallocation request including determining whether to grant the requestwith the requested allocation of electric current (or at least a portionof the requested allocation of electric current). The circuit sharingcontroller 305 can determine whether to grant the request and whatamount of electric current to allocate in different ways in differentembodiments of the invention. In one embodiment, a load sharing processis used where multiple charging stations that are wired to the sameelectrical circuit can share the load of the circuit such that each ofthose charging stations are allocated an amount of electric current andthe sum of the allocated electric current does not exceed the capacityof the circuit. An exemplary load sharing process will be described ingreater detail with respect to FIGS. 5A-B and 6. In another embodiment,a time sharing process is used where multiple charging stations that arewired to the same electrical circuit take turns drawing power from thepower grid (not necessarily equally) such that the capacity of thecircuit is not exceeded. An exemplary time sharing process will bedescribed in greater detail with respect to FIGS. 7-9.

FIGS. 5A-B are flow diagrams illustrating exemplary operations for acircuit sharing process based on load sharing according to oneembodiment of the invention. In one embodiment, the operations describedin reference to FIGS. 5A-B are performed by the circuit sharingcontroller 305. FIGS. 5A-B will be described with reference to theexemplary embodiment of FIG. 3 and will be described with reference tothe charging station 120 requesting an allocation of electric current.

At block 510, the circuit sharing controller 305 receives a request foran allocation of current from the charging station 120 in the wiringgroup 350. The request may indicate the amount of electric currentrequested. Flow moves from block 510 to block 515. At block 515, thecircuit sharing controller 305 determines the attributes of the wiringgroup 350 including the maximum amount of current supported by thewiring group 350 (the maximum amount of current supported by the circuitbreaker 125) and the amount of current that is presently allocated tothe wiring group 350. It should be understood that the amount of currentpresently allocated to the wiring group 350 can be distributed amongzero or more of the charging stations in the wiring group 350. That is,there may not be any current allocated to the wiring group 350 or thecurrent may be allocated to one or more members of the wiring group 350.Flow moves from block 515 to block 520.

At block 520, the circuit sharing controller 305 determines whethergranting the request for the requested amount of current would exceedthe maximum amount of current supported by the wiring group 350. If thegrant would exceed the maximum amount of current that the wiring group350 supports, flow moves to block 540 (which will be discussed in moredetail with reference to FIG. 5B), otherwise flow moves to block 525. Atblock 525 the circuit sharing controller 305 updates the amount ofelectric current presently allocated for the wiring group 350 by therequested amount. Flow moves from block 525 to block 530. At block 530,the circuit sharing controller 305 generates and transmits a set currentallocation message to the charging station 120 that indicates a grant ofthe request for the full amount of the requested allocation of current.With reference to FIG. 4, the circuit sharing controller 305 transmitsthe set current allocation message to the charging station 120 atoperation 4.3.

Sometime after receiving the set current allocation message, thecharging station 120 sets its power draw according to the set currentallocation message at operation 4.4. For example, with reference to FIG.2, the charging station control modules 205 cause the electricitycontrol device 210 to energize the charging point connection 155. If theset current allocation message includes an amount of current to allocate(e.g., an upper limit on the amount of current that the charging station120 can consume from, or provide to, the power grid 130), the chargingstation control modules 205 cause the electricity control device 210 toset that particular amount of power draw. For example, the electricitycontrol device 210 can include circuitry to variably control the amountof power draw (e.g. Pulse Width Modulation (PWM) circuitry). Aftersetting the power draw, the charging station 120 transmits a setelectric current acknowledgement message to the circuit sharingcontroller 305 at operation 4.5.

With reference to FIG. 5B, at block 540 the circuit sharing controller305 determines the amount of electric current that is presentlyallocated to each of the charging stations in the wiring group 350. Flowmoves from block 540 to block 545, where the circuit sharing controller305 adjusts the amount of electric current that is allocated to one ormore of those charging stations such that the requesting chargingstation can be allocated at least a portion of the requested amount ofelectric current. In one embodiment, the circuit sharing controller 305adjusts the electric current allocations of each of the chargingstations in the wiring group 350 such that a substantially equivalentamount of electric current is allocated to each of the active chargingstations (as used herein, an active charging station is a chargingstation that is allocated more than a relatively small amount ofelectric current and currently has a charging session).

In other embodiments, the circuit sharing controller 305 adjusts theelectric current allocations of one or more of the active chargingstations based on a set of one or more charging session attributes thatinclude information about each of the charging sessions on the activecharging stations. In such an embodiment, the adjustment does notnecessarily result in each of the active charging stations beingallocated a substantially equivalent amount of electric current. Thecharging session attributes can include charging session duration, thetype of account associated with the charging session (e.g., privilege ofthe account), percentage of charge complete, percentage of chargeremaining, battery temperature of the electric vehicle, time remainingon the charging session, priority of the charging session, etc. By wayof example and not limitation, the circuit sharing controller 305 can beconfigured to more greatly reduce the electric current allocation of acharging station that has a charging session that has been operatinglonger than another charging station that has a charging session on thesame electrical circuit. As another example, the circuit sharingcontroller 305 adjusts the electric current allocations based on theprivilege of the accounts associated with charging sessions on thecharging stations (e.g., an account with a higher privilege can beallocated a relatively higher amount of electric current than an accountwith a lower privilege).

Flow moves from block 545 to block 550 where the circuit sharingcontroller 305 generates and transmits a set current allocation messageto each of those one or more charging stations to instruct thosecharging stations to set the amount of electric current they are drawingto the amount the circuit sharing controller 305 has allocated. Thus,each set current allocation message indicates the amount of electriccurrent that has been allocated to a charging station. Upon receipt of aset current allocation message, the charging station 120 sets its powerdraw (e.g., the maximum amount of electricity it can draw from the powergrid 130).

The charging stations can set (e.g., reduce or increase) the amount ofelectric current they are drawing in different ways in differentembodiments. In one embodiment, the electricity control device 210 inthe charging station 120 includes circuitry and electronics to variablycontrol the output of the charging station (e.g., using Pulse WidthModulation (PWM)). In another embodiment, the charging stations cancontrol the amount of current drawn by an electric vehicle via acommunication link between the charging stations and the electricvehicle (e.g., through a SAE 1772 interface). In such an embodiment, theelectric vehicles accept a charging cord that connects control signalsfrom the charging station that instructs the electric vehicle e how muchcurrent the charging station can supply (e.g., how much current at220V).

Flow moves from block 550 to block 555. At block 555, the circuitsharing controller 305 determines for each of the charging stations thathave been sent a set current allocation message, whether anacknowledgement message has been received from that charging station(the acknowledgement message indicating the power draw has been set inaccordance with the set allocation message). If an acknowledgementmessage has not been received, flow moves to block 560 where alternativeaction is taken. For example, the alternative action can includeretransmitting the set current allocation message a number of times. Ifan acknowledgement message is still not received after retransmittingthe set current allocation message the number of times, the alternativeaction can include transitioning back to block 540 to begin the processof reallocating the electric current with the assumption that thecharging station(s) that have not replied are capable of drawingelectric current at their full electric current allocation (theirpresent electric current allocation) and cannot be adjusted). Ifacknowledgement messages have been received, then flow moves to block565.

At block 565, the circuit sharing controller 305 updates the amount ofcurrent allocated for the wiring group and for each of the activecharging stations in the wiring group (at least those charging stationsthat have adjusted their electric current allocation). Flow moves fromblock 565 to block 570, where the circuit sharing controller 305generates and transmits a set allocation message to the requestingcharging station which indicates an amount of electric current that hasbeen allocated to that charging station. Upon receipt of a set currentallocation message, the requesting charging station sets its power drawin accordance with the set current allocation message.

FIG. 6 is a flow diagram illustrating exemplary operations fordynamically adjusting electric current allocations of multiple chargingstations on the same electrical circuit when a charging station nolonger requests an allocation of current according to one embodiment ofthe invention. FIG. 6 will be described with reference to the exemplaryembodiment of FIG. 3. In one embodiment, the operations described inFIG. 6 are performed by the circuit sharing controller 305.

At block 610, the circuit sharing controller 305 receives a message froma charging station (e.g., the charging station 120) indicating that anallocation of current is no longer requested. For example, the messagecan be sent as a result of the charging session ending (e.g., thevehicle operator 110 ending the charging session), the charging sessioncompleted (or substantially completed), etc. Flow then moves to block615 where the circuit sharing controller 305 determines the attributesof the wiring group of the charging station (the wiring group 350)including the maximum amount of current supported by the wiring group350 (the maximum amount of current supported by the circuit breaker 125)and the amount of electric current that is presently allocated to thewiring group 350. Flow then moves to block 620.

At block 620, the circuit sharing controller 305 reduces the amount ofcurrent that is presently allocated to the wiring group by at least aportion of the amount that was allocated to the charging station (arelatively small amount of current may remain allocated to the chargingstation). Thus, the circuit sharing controller 305 returns at least aportion of the amount of current that was allocated to the chargingstation to the wiring group (that is, the at least a portion of theallocated amount can be allocated to different ones of the chargingstations in the wiring group). Flow moves from block 620 to block 625.

At block 625, the circuit sharing controller 305 determines whether anyof the charging stations that currently have active charging sessionshave an allocated amount of current below their maximum level. If no,then flow moves to block 630 where the process exists. If there are oneor more charging stations that currently have active charging sessionsthat are allocated an amount less then their maximum level, then flowmoves to block 635.

At block 635, the circuit sharing controller 305 increases the amount ofallocated current to one or more of those charging stations from theamount of current returned to the wiring group. In one embodiment theamount of allocated current is substantially equally distributed acrossthe one or more charging stations. In another embodiment, the amount ofcurrent returned to the wiring group is allocated to those chargingstations based on a set of one or more charging session attributes(e.g., charging session duration, type of account associated with thecharging session (e.g., privilege of the account), percentage of chargecomplete, battery temperature of the electric vehicle, percentage ofcharge remaining, time remaining on the charging session, priority ofthe charging session, etc.). Flow moves from block 635 to block 640. Atblock 640, the circuit sharing controller 305 generates and transmits aset allocation message to each of those charging stations to increasetheir amount of electric current allocation.

In the event of the circuit sharing controller 305 losing connectivitywith member(s) of the wiring group 350, those charging stations in thewiring group 350 maintain their present allocations. For example, acharging station with an electric current allocation of 15 A willmaintain that allocation upon losing connectivity with the circuitsharing controller 305 until connectivity is re-established regardlessof whether that charging station is active or idle. In some embodiments,a relatively small amount of electric current is allocated to each ofthe charging stations in the wiring group 350 so that each of thecharging stations can at least minimally supply current to electricvehicles in case of a failure of the circuit sharing controller 305 or aloss of network connectivity with the circuit sharing controller 305.

While FIGS. 5A-B and 6 describe an circuit sharing process based on thecharging stations sharing the load of the electrical circuit when thecircuit would otherwise be overloaded, in some embodiments the circuitsharing mechanism is based on a time sharing process. For example, atime sharing process can be used when charging stations do not have thecapability of throttling their power draw (e.g., the electricity controldevice either energizes or de-energizes the charging point connectionand thus the charging point connection can either draw either all of thepower draw it is rated for or no power draw). For example, withreference to FIG. 2, the electricity control device 210 energizes andde-energizes the charging point connection 155 but does not include (ordoes not implement) an electric current throttling mechanism.

In some embodiments, a time sharing process is used to control the dutycycle of the charging station output such that each of the chargingstations in a wiring group can take turns drawing power from the powergrid while not exceeded the maximum capacity of the electrical circuitbased on a time sharing process. In the time sharing process describedherein, a charging station is typically in one of the following threestates: idle, electric current allocated, and waiting for electriccurrent allocation. In the idle state, an electric vehicle is notcoupled with the charging station and a charging session is not active(thus the charging station is not being used). In the electric currentallocated state, the charging station is presently allocated electriccurrent and a charging session is active. Electric current can be drawnfrom the power grid in the electric current allocated state. In thewaiting for electric current allocation state, a charging session isactive; however electric current is not presently allocated and thecharging station is not authorized to draw current from the power grid.

FIG. 7 is a flow diagram illustrating exemplary operations forperforming a circuit sharing process that is based on time sharingaccording to one embodiment of the invention. FIG. 7 will be describedwith reference to the exemplary embodiment of FIG. 3. In one embodiment,the operations described in FIG. 7 are performed by the circuit sharingcontroller 305.

At block 710, the circuit sharing controller 305 receives a request froma charging station for an allocation of current. For purposes ofexplanation, FIG. 7 will be described with reference to the circuitsharing controller 305 receiving the request from the charging station120. Flow then moves to block 715, where the circuit sharing controller305 determines the wiring group of the charging station 120 if necessary(if the circuit sharing controller 305 is providing service for a singlewiring group then that wiring group is assumed) and the current chargingconfiguration of the wiring group including the capacity of the circuitof the wiring group (e.g., the maximum amount of current supported bythe wiring group) and the amount of current that is presently allocatedto the wiring group (to members of the wiring group). As part of thecharging configuration, the circuit sharing controller 305 alsodetermines the amount of current the charging station 120 supplies(different charging stations in the wiring group 350 can supply adifferent amount of current in some embodiments). Flow moves from block715 to block 720.

At block 720, the circuit sharing controller 305 determines whethergranting the request (e.g., allowing the charging station 120 toenergize the charging point connection 155 and supply the maximum amountof current to the electric vehicle 110) would cause the capacity of theelectrical circuit to be exceeded. If the capacity would be exceeded,then flow moves to block 740, otherwise flow moves to block 725.

At block 725, the circuit sharing controller 305 updates the amount ofcurrent that is allocated for the wiring group. Flow moves from block725 to block 730 where the circuit sharing controller 305 generates andtransmits a message to the charging station 120 indicating a grant ofthe request. Upon receipt of the message, the charging station 120energizes the charging point connection 155 to allow electricity to flowbetween the power grid 130 and the electric vehicle 110.

At block 740 (the capacity of the circuit would be exceeded), thecircuit sharing controller 305 cyclically reallocates the current amongthe charging stations in the wiring group such that each chargingstation has a turn of receiving current over a time period (at leastthose charging stations that have an active charging session). That is,the circuit sharing controller 305 cycles through the charging stationsin the wiring group such that each of those charging stations can supplycurrent for a certain amount of time in a given time period.

The cyclical reallocation of electric current can be performeddifferently in different embodiments of the invention. FIG. 8 is a flowdiagram illustrating exemplary operations for cyclically reallocatingelectric current according to one embodiment of the invention. In oneembodiment, the operations described in FIG. 8 are part of the operationof block 740.

At block 810, the circuit sharing controller 305 sets the requestingcharging station as a charging station that is presently waiting forelectric current allocation. Other charging station(s) in the wiringgroup 350 may also be presently waiting for electric current allocation.Flow then moves to block 820, where the circuit sharing controller 305determines the number of charging stations that can be actively chargingin the wiring group 350 at a given time. By way of example and notlimitation, if each charging station of the wiring group 350 supplies 15A of current, and the circuit has a capacity of 50 A, then threecharging stations can be actively charging at any given time withoutoverloading the capacity of the circuit. In some embodiments, theoperation described in block 820 is optional. Flow moves from block 820to block 830.

At block 830, the circuit sharing controller 305 selects one of thecharging station(s) that presently is allocated current (thus is in theelectric current allocated state). The circuit sharing controller 305can select that charging station in different ways in differentembodiments (e.g., a random selection, a sequential selection, aselection based on one or more charging session attributes (e.g.,charging session duration, type of account associated with the chargingsession (e.g., privilege of the account), percentage of charge complete,percentage of charge remaining, battery temperature of the electricvehicle, time remaining on the charging session, priority of thecharging session, etc.), etc.). Flow moves from block 830 to block 840.

At block 840, the circuit sharing controller 305 generates and transmitsa message to that selected charging station in the electric currentallocated state. The message instructs that charging station to suspendthe charging session and cease drawing current from the power grid 130.Thus, the message is an attempt by the circuit sharing controller 305 totransition the selected charging station from the electric currentallocated state to the waiting for electric current allocation state.

Flow moves from block 840 to block 845 where the circuit sharingcontroller 305 waits to receive an acknowledgement message from thatcharging station that indicates that it has suspended the chargingsession and ceased drawing current from the power grid 130. If thecircuit sharing controller 305 receives such an acknowledgement message,then flow moves to 860, otherwise flow moves to block 850.

At block 850 (an acknowledgement message has not been received), thecircuit sharing controller 305 takes alternative action. The alternativeaction can include retransmitting the message to the selected chargingstation a number of times. If the circuit sharing controller 305 stilldoes not receive an acknowledgement message, the circuit sharingcontroller 305 assumes that the selected charging station is activelycharging (or is capable of drawing its maximum amount of current fromthe power grid 130) and flow moves back to block 830 where the circuitsharing controller 305 selects a different charging station that is inthe electric current allocated state.

At block 860, the circuit sharing controller 305 selects one of thecharging station(s) that are waiting for electric current allocation.The circuit sharing controller 305 can select the charging station indifferent was in different embodiments. For example, the chargingstation that has been waiting the longest for an allocation of currentcan be selected. As another example, the selected charging station canbe based one or more charging session attributes (e.g., charging sessionduration, the type of account associated with the charging session(e.g., privilege of the account), percentage of charge complete,percentage of charge remaining, battery temperatures of the electricvehicles, time remaining on the charging session, priority of thecharging session, etc.). Flow moves from block 860 to block 865.

At block 865, the circuit sharing controller 305 generates and transmitsa message to the selected charging station that authorizes that chargingstation to draw current from the power grid 130. The circuit sharingcontroller 305 also sets that selected charging station as being in theelectric current allocated state. Upon receipt of the message, thecharging station can resume (or initiate) its charging session andenergize its charging point connection and draw current from the powergrid 130. Flow moves from block 865 to block 870, where the circuitsharing controller 305 waits for a time period to expire. If the timeperiod has expired, then flow moves back to block 830.

Thus, multiple charging stations can share the same electrical circuitwithout overloading the capacity of that circuit by using the timesharing process described above. In some embodiments the chargingstations are treated equally (e.g., a round-robin approach) while inother embodiments the charging stations can be treated differently basedon one or more charging session attributes (e.g., charging sessionduration, the type of account associated with the charging session(e.g., privilege of the account), percentage of charge complete,percentage of charge remaining, battery temperature of the electricvehicle, time remaining on the charging session, priority of thecharging session, etc.).

FIG. 9 is a flow diagram illustrating exemplary operations performed ina circuit sharing process that is based on time sharing when a chargingstation no longer requests an allocation of current according to oneembodiment of the invention. FIG. 9 will be described with reference tothe exemplary embodiment of FIG. 3. In one embodiment, the operationsdescribed with reference to FIG. 9 are performed by the circuit sharingcontroller 305.

At block 910, the circuit sharing controller 305 receives a message froma charging station that indicates that an allocation of current is nolonger requested. For purposes of explanation, FIG. 9 will be describedwith reference to the circuit sharing controller 305 receiving themessage from the charging station 120. The message can indicate that thecharging session has ended (e.g., the vehicle operator 145 has ended thecharging session) or that charging has been completed or substantiallycompleted (e.g., the charging station 120 has measured a relativelysmall amount of current transferred to the electric vehicle over acontinuous amount time, etc.). Flow moves from block 910 to block 915.

At block 915, the circuit sharing controller 305 determines the wiringgroup for the charging station 120 if appropriate (if the circuitsharing controller 305 is providing service for multiple wiring groups)and the current charging configuration of the wiring group (e.g., which(if any) of the charging stations of the wiring group 350 presently havean allocation of current, which (if any) of the charging stations of thewiring group 350 are presently waiting for an allocation of current,which (if any) of the charging stations of the wiring group 350 areidle, the capacity of the electrical circuit, etc.). Flow moves fromblock 915 to block 920.

At block 920, the circuit sharing controller 305 determines whether thecharging station 120 presently is allocated current. If the chargingstation 120 is presently allocated current, then flow moves to block925, otherwise flow moves to block 940 where the charging station 120 isremoved from the group of charging station(s) that are currently waitingfor an allocation of current. At block 925, the circuit sharingcontroller 305 de-allocates the current from the charging station 120and reduces the amount of current that is presently allocated to thewiring group 350 (e.g., returns that amount of current). Flow then movesto block 930 where the circuit sharing controller 305 determines whetherthere are other charging station(s) that are waiting for an allocationof current in the wiring group 350. If there are none, then flow movesto block 935 where the process exits, otherwise flow moves back to block860 of FIG. 8 and the current that was allocated to the charging station120 can be allocated to one of the other charging station(s) that arewaiting for an allocation of current.

In the event of the circuit sharing controller 305 losing connectivitywith one or more charging stations of the wiring group 350, each ofthose charging stations maintain their present state. For example,charging stations in the electric current allocated state remain in thatstate with that amount of electric current being allocated and thosecharging stations that are in the waiting for electric currentallocation state remain waiting for electric current allocation untilconnectivity is restored with the circuit sharing controller 305.

FIG. 10 illustrates an exemplary embodiment of the circuit sharingcontroller 305 according to one embodiment of the invention. Asillustrated in FIG. 10, the circuit sharing controller 305 includes thetransceivers (wired and/or wireless) 1030 coupled with one or morecircuit sharing control modules 1020. The one or more circuit sharingcontrol modules 1020 are coupled with the one or more charging stationconfiguration structure(s) 1040. The circuit sharing control module(s)1020 perform the circuit sharing mechanism described herein (e.g., loadsharing and/or time sharing for different wiring groups). Currentallocation messages are exchanged between the charging stations 1050 andthe transceiver(s) 1030 (e.g., current allocation request messages,current allocation set messages, acknowledgement messages, etc.). Thecharging station configuration structure(s) 1040 stores charging stationconfiguration information (e.g., for each charging station, the wiringgroup for that charging station, the capacity of the electrical circuitof that wiring group, a trip margin, a quantity of electric currentallocated for members of that wiring group, whether a vehicle is pluggedinto the charging station, the duration of charging session (current andpast), etc.).

Embodiments of the invention described herein can reduce the cost of thepower distribution infrastructure needed to deploy charging stations.For example, the number of service drops and meters, the amount of heavygauge wiring, etc., can be reduced. Additionally, the need for powerutilities to add or replace local transformers to support the load ofthe charging stations is also reduced.

In some embodiments of the invention, the electric current allocationrequest messages also include information for authorizing the vehicleoperator associated with the charging session. If the vehicle operatoris not authorized, that charging station will not be allocated electriccurrent.

While embodiments of the invention have described a centrally locateddevice controlling the electric current allocations for a wiring (e.g.,the circuit sharing controller 305 controlling the electric currentallocations for the wiring group 350), in other embodiments the circuitsharing mechanism is distributed among the charging stations in a wiringgroup (e.g., distributed amount the charging stations 120, 310, 315,325, and 330 of the wiring group 350).

While the flow diagrams in the figures show a particular order ofoperations performed by certain embodiments of the invention, it shouldbe understood that such order is exemplary (e.g., alternativeembodiments may perform the operations in a different order, combinecertain operations, overlap certain operations, etc.)

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

What is claimed is:
 1. A method comprising: receiving a first message that indicates a request for an allocation of electric current through a first charging equipment, wherein the first charging equipment shares a current capacity with a second charging equipment, and wherein at a time of receipt of the first message the second charging equipment is presently allocated electric current; determining that granting the request would exceed the current capacity and responsive to that determination, adjusting the electric current allocated to the second charging equipment such that the first charging equipment can be allocated electric current and the and the current capacity is not exceeded; granting the request and allocating electric current to the first charging equipment.
 2. The method of claim 1, wherein the first message includes a requested amount of electric current, and wherein allocating electric current to the first charging equipment includes allocating the requested amount of electric current.
 3. The method of claim 1, further comprising: wherein adjusting the electric current allocated to the second charging equipment includes transmitting a second message to the second charging equipment that indicates a first amount of current that is allowed to be drawn through the second charging equipment, wherein the first amount of current is a reduction from a most previous allocation of current for the second charging equipment; prior to granting the request and allocating electric current to the first charging equipment, receiving an acknowledgement message that indicates that the second charging equipment is limiting current draw in accordance with the second message; and wherein allocating electric current to the first charging equipment includes transmitting a third message to the first charging equipment that indicates a second amount of current that is allowed to be drawn through the first charging equipment.
 4. The method of claim 1, further comprising: cyclically reallocating electric current among the first charging equipment and the second charging equipment in a time period such that each of the first charging equipment and the second charging equipment receives an allocation of current in that time period while not exceeding the current capacity.
 5. The method of claim 1, further comprising: receiving a second message that indicates that electric current allocation is no longer required at the second charging equipment; and responsive to receiving that message, redistributing the electric current that is allocated to the second charging equipment to the first charging equipment.
 6. The method of claim 1, wherein adjusting the electric current allocated to the second charging equipment and allocating electric current to the first charging equipment is further based on a set of one or more charging session attributes associated with a first charging session for a first electric vehicle connected to the first charging equipment and a second charging session for a second electric vehicle connected to the second charging equipment, wherein the set of charging session attributes includes for each charging session one or more of charging session duration, type of account associated with that charging session, percentage of charging complete, percentage of charging remaining, battery temperature of the electric vehicle, priority of that charging session, and time remaining on that charging session.
 7. An apparatus, comprising: a controller coupled with a first charging equipment and a second charging equipment that share a current capacity, the controller configured to perform the following: limit a total amount of current drawn through the first charging equipment and the second charging equipment to not exceed the current capacity including: communicate a first current limit to the first charging equipment to cause a first electric vehicle to limit its current draw to not exceed the first current limit, communicate a second current limit to the second charging equipment to cause a second electric vehicle to limit its current draw to not exceed the second current limit, wherein a sum of current to be drawn at the first current limit and the second current limit does not exceed the current capacity.
 8. The apparatus of claim 7, wherein the communicated first current limit is to cause the first electric vehicle to limit its current draw to not exceed the first current limit through modulation of a first signal from the first charging equipment to the first electric vehicle to communicate the first current limit to the first electric vehicle, and wherein the communicated second current limit is to cause the second electric vehicle to limit its current draw to not exceed the second current limit through a modulation of a second signal from the second charging equipment to the second electric vehicle to communicate the second current limit to the second electric vehicle.
 9. The apparatus of claim 7, wherein the first current limit and the second current limit are substantially equal.
 10. The apparatus of claim 7, wherein the first current limit is less than the second current limit.
 11. The apparatus of claim 7, wherein the controller is further configured to reallocate current upon a determination that electric current is no longer required to be drawn by the first electric vehicle including to communicate a third current limit to the second charging equipment to cause the second electric vehicle to limit its current draw to not exceed the third current limit, wherein the third current limit is greater than the second current limit, and wherein current to be drawn at the third current limit does not exceed the current capacity.
 12. The apparatus of claim 7, wherein the controller is further configured to: dynamically adjust the first current limit and the second current limit based on one or more of the following: a percentage of charging completed by the first electric vehicle and the second electric vehicle; a percentage of charging remaining of the first electric vehicle and the second electric vehicle; a duration of charging of the first electric vehicle and the second electric vehicle; and a type of account associated with the first electric vehicle and the second electric vehicle. 